Polyimide

Polyimide is one of the toughest plastics there is. It stays strong from far below freezing to over 300 °C, doesn't melt, and shrugs off most chemicals. Its best-known form is Kapton, DuPont's amber film from the 1960s.

It's made in two steps from two building blocks, pyromellitic dianhydride and oxydianiline. First they're stirred together in a solvent at room temperature. Each oxydianiline end hooks onto a dianhydride end, and the molecules link into long chains, forming a thick, honey-like solution called polyamic acid. This is spread out as a film or coating, then heated to around 300 °C, which drives off water and closes each link into a stiff ring, the imide. Now it can no longer melt or dissolve.

In a TV it has two very different roles. As a film tens of micrometers thick, it's the bendable base of each flexible printed circuit. As a coating about 50 to 100 nanometers thick, it lines the inside of both glass sheets in the LCD panel. There, the surface is rubbed with a velvet-like cloth or exposed to polarized UV light to give it a direction, and the liquid crystal molecules line up along it. Display makers tune their own recipes.